1. Field of the Invention
This invention relates to ballistic resistant composite articles. More particularly, this invention relates to such articles having improved ballistic protection.
2. Prior Art
Ballistic articles such as bulletproof vests, helmets, structural members of helicopters and other military equipment, vehicle panels, briefcases, raincoats and umbrellas containing high strength fibers are known. Fibers conventionally used include aramid fibers such as poly(phenylenediamine terephthalamide), graphite fibers, nylon fibers, ceramic fibers, glass fibers and the like. For many applications, such as vests or parts of vests, the fibers are used in a woven or knitted fabric. For many of the applications, the fibers are encapsulated or embedded in a matrix material.
In “The Application of High Modulus Fibers to Ballistic Protection”, R. C. Laible et al., J. Macromol. Sci.-Chem., A7(1), pp. 295-322, 1973, it is indicated on p. 298 that a fourth requirement is that the textile material have a high degree of heat resistance. In an NTIS publication, AD-A018 958 “New Materials in Construction for Improved Helmets”, A. L. Alesi et al., a multilayer highly oriented polypropylene film material (without matrix), referred to as “XP”, was evaluated against an aramid fiber (with a phenolic/polyvinyl butyral resin matrix). The aramid system was judged to have the most promising combination of superior performance and a minimum of problems for combat helmet development. U.S. Pat. No. 4,403,012 and U.S. Pat. No. 4,457,985 disclose ballistic resistant composite articles comprised of networks of high molecular weight polyethylene or polypropylene fibers, and matrices composed of olefin polymers and copolymers, unsaturated polyester resins, epoxy resins, and other resins curable below the melting point of the fiber.
A. L. Lastnik, et al., “The Effect of Resin Concentration and Laminating Pressures on KEVLAR Fabric Bonded with Modified Phenolic Resin”, Tech. Report NATICK/TR-84/030, Jun. 8, 1984; disclose that an interstitial resin, which encapsulates and bonds the fibers of a fabric, reduces the ballistic resistance of the resultant composite article.
U.S. Pat. Nos. 4,623,574 and 4,748,064 disclose a simple composite structure comprising high strength fibers embedded in an elastomeric matrix. The simple composite structure exhibits outstanding ballistic protection as compared to simple composites utilizing rigid matrices, the results of which are disclosed in the patents. Particularly effective are simple composites employing ultra-high molecular weight polyethylene and polypropylene such as disclosed in U.S. Pat. No. 4,413,110.
U.S. Pat. Nos. 4,737,402 and 4,613,535 disclose complex rigid composite articles having improved impact resistance which comprise a network of high strength fibers such as the ultra-high molecular weight polyethylene and polypropylene disclosed in U.S. Pat. No. 4,413,110 embedded in an elastomeric matrix material and at least one additional rigid layer on a major surface of the fibers in the matrix. It is disclosed that the composites have improved resistance to environmental hazards, improved impact resistance and are unexpectedly effective as ballistic resistant articles such as armor.
U.S. Pat. No. 4,650,710 discloses a ballistic resistant fabric article which comprises at least one network of fibers selected from the group consisting of extended chain polyethylene, polypropylene, polyvinyl alcohol and polyacrylonitrile fibers coated with a low modulus elastomeric material.
U.S. Pat. No. 4,650,710 discloses a flexible article of manufacture comprising a plurality of first flexible layers arranged in a first portion of the article, each of said first layers consisting essentially of fibers having a tensile modulus of at least about 300 g/denier and a tenacity of at least about 15 g/denier and a tenacity of at least about 15 g/denier and a plurality of a second flexible layer arranged in a second portion of said article, each of said second flexible layers comprising fibers, the resistance to displacement of fibers in each of said second flexible layers being greater than the resistance to displacement in each of said first flexible layers.
Other ballistic resistant articles are described in U.S. Pat. Nos. 4,916,000, 4,403,012, 4,457,985, 4,737,401, 4,543,286, 4,563,392 and 4,501,856.